The goal of this project is to maintain a cell bank and DNA repository for marrow transplant patients and unrelated donors and maintain a detailed HLA data base incorporating the molecular data that is not routinely reported by the clinical typing laboratory. The research objective is to determine the clinical relevance of matching for class I HLA-A, B, C molecular variants and the new class I HLA-E, F and G genes. The core component of this project will be responsible for accumulating cells and DNA from patients and unrelated donors, and generating as needed EBV-transformed B-lymphoblastoid cell lines (LCL) for special studies. Research data will be collected and integrated with the Division of Clinical Research's Clinical Marrow Transplant Data Base. As data are acquired to define the polymorphism for MHC class I and class II loci, appropriate statistical analysis will be undertaken periodically to assess whether the prevalence of disparity for any given locus is sufficient to allow calculations of informative clinical correlations. The eventual clinical analysis will be performed with the combined data using multivariate methods with the goals of determining the impact of HLA incompatibility on graft rejection and the incidence and severity of GVHD.